A mechanical seal assembly is commonly used on a rotating shaft of a motor enclosed in a motor housing, and projecting through a seal housing adjacent the motor housing to prevent water or other fluid from migrating along the shaft and entering the seal and motor housings. One such known application involves a driven seal assembly mounted in a seal housing about the rotating shaft of an electric motor drivingly connected to an impeller of a fountain aerator having its motor housing disposed in a body of water.
Such prior art driven seal assemblies include a pair of stationary seal seats, a pair of rotary seals and a coil spring, all of which are mounted on a shaft driven by the motor. Typically, one stationary seal seat is fixedly mounted in a bore of the seal housing and cooperates with one of the rotary seals. The other stationary seal seat is fixed in a bore of the motor housing and cooperates with the other of the rotary seals. Both rotary seals have internal rubber surfaces that are frictionally fit upon the outer diameter of the shaft so that the rotary seals will rotate with the shaft and provide inner seals along the shaft to prevent water from migration therealong. To maintain a seal between the opposed seal faces of the rotary seals and the stationary seat seals and thus seal the bores in the seal and motor housings, the coil spring is placed under compression between the two rotary seals.
Certain problems may arise with using this type of driven seal assembly on a driven motor shaft. For example during motor operation, the rotary seals are driven by friction of rubber against the shaft. If the friction fit begins to slip, heat is generated and a groove will begin to be worn into the shaft. The rubber surfaces of the rotary seals become glazed, locking of the stationary seal seats and rotary seals may occur, the supple fit of the rotary seals is lost and wear on the shaft will enable water to enter the motor housing and destroy the motor.
Accordingly, there is a need to provide a driven seal assembly that overcomes the problems of the prior art and ensures proper sealing of a rotating shaft relative to seal and motor housings is maintained for prolonged operation of the motor.